PR review

Replace fragile price change detection in Purchase.save() with a
lazy dirty flag approach. A pre_save/post_save signal pair detects
price/currency changes without extra DB queries, and convert_prices()
uses the flag to determine which purchases need conversion.

- Add needs_price_update BooleanField with db_index
- Add pre_save signal to store old price/currency values
- Add post_save signal to set needs_price_update=True when price/currency changes
- Simplify Purchase.save() to remove DB reload + comparison logic
- Remove price_or_currency_differ_from() method
- Update convert_prices() to filter on needs_price_update flag
- Extract _get_exchange_rate() and _save_converted_price() helpers
- Add tests for the new behavior

STATUSES.md

@@ -0,0 +1,157 @@
+# Game & Purchase Status Definitions
+
+## Game Statuses
+
+Games have a `status` field with the following values:
+
+| Status | Code | Description |
+|--------|------|-------------|
+| **Unplayed** | `u` | Game was purchased but never played |
+| **Played** | `p` | Game was played but not yet finished |
+| **Finished** | `f` | Game has been completed |
+| **Retired** | `r` | Game was intentionally retired (e.g., no longer accessible, collector's item) |
+| **Abandoned** | `a` | Game was played but the user gave up on it |
+
+**Setting game status:**
+- Users explicitly set game status via the UI (finish/drop purchase buttons, status change form)
+- Status changes are tracked in `GameStatusChange` model
+- Refunding a purchase always marks its games as abandoned
+
+---
+
+## Purchase-Level Status Concepts
+
+These concepts determine whether a purchase appears in the "unfinished" or "dropped" lists in stats views.
+
+### Finished
+
+A purchase is considered **finished** when:
+
+```
+Game.status == "f" OR Purchase.games.* has a PlayEvent with an ended date
+```
+
+Either signal indicates the game is complete:
+- **Explicit**: User marked the game as finished (`Game.status = "f"`)
+- **Implicit**: A PlayEvent exists with `ended` date set (data-driven)
+
+This uses **OR** logic during a transition period. Later, these signals should be kept in sync so only one source of truth is needed.
+
+### Dropped
+
+A purchase is considered **dropped** when:
+
+```
+Game.status == "a" OR Purchase.date_refunded IS NOT NULL
+```
+
+Either signal indicates the user no longer has an active interest in the game:
+- **Explicit**: User marked the game as abandoned (`Game.status = "a"`)
+- **Implicit**: User refunded the purchase (which automatically sets games to abandoned)
+
+Note: Refunding a purchase always marks its games as abandoned. There is no option to refund without abandoning.
+
+---
+
+## Unfinished vs. Dropped
+
+The stats views categorize purchases into **unfinished** and **dropped** lists.
+
+### Unfinished
+
+A purchase is **unfinished** when:
+1. It was purchased in the relevant time period (this year for yearly stats, all time for all-time stats)
+2. It was NOT refunded (only counts toward unfinished/backlog)
+3. It is NOT finished (per the finished definition above)
+4. It is NOT dropped (per the dropped definition above)
+5. It is NOT infinite (subscription, etc.)
+6. It IS a game or DLC (not season passes or battle passes)
+
+**Unfinished = Active backlog** — games the user may still play.
+
+### Dropped
+
+A purchase is **dropped** when:
+1. It was purchased in the relevant time period
+2. It is NOT finished (per the finished definition above)
+3. It matches at least one dropped signal (per the dropped definition above)
+4. It is NOT infinite
+5. It IS a game or DLC
+
+**Dropped = Terminal state** — games the user has given up on or refunded.
+
+### Summary Table
+
+| Category | Includes Refunded? | Key Condition |
+|----------|-------------------|---------------|
+| **Unfinished** | No | NOT finished, NOT dropped |
+| **Dropped** | Yes | Finished OR Abandoned/Retired |
+| **Refunded** | Yes | `date_refunded IS NOT NULL` |
+| **Infinite** | Yes | `infinite = True` |
+
+---
+
+## Query Patterns
+
+### Checking if a game is finished
+
+```python
+game.finished()  # Returns True if status="f" or has PlayEvent with ended date
+```
+
+### Checking if a game is abandoned
+
+```python
+game.abandoned()  # Returns True if status="a"
+```
+
+### Getting finished purchases
+
+```python
+Purchase.objects.finished()  # All purchases where games are finished
+```
+
+### Getting dropped purchases
+
+```python
+Purchase.objects.dropped()  # All purchases that are abandoned or refunded
+```
+
+---
+
+## Transition State
+
+The system uses **OR logic** for both finished and dropped to catch any mismatch between explicit user actions and data signals:
+
+- **Finished**: `status="f" OR PlayEvent.ended`
+- **Dropped**: `status="a" OR date_refunded`
+
+This bridges the gap between the old model (where `date_finished` and `date_dropped` were on the Purchase model) and the new model (where `Game.status` and `PlayEvent` are the sources of truth).
+
+**Future:** These signals should be kept in sync. For example:
+- Setting `Game.status = "f"` should create a PlayEvent with `ended` date
+- When the sync is reliable, the OR can be simplified to a single check
+
+Note: Refunding a purchase always automatically sets its games' status to Abandoned. This is not optional — there is no way to refund without abandoning.
+
+---
+
+## Edge Cases
+
+### Unplayed games
+- Unplayed games (`status="u"`) are considered **unfinished**, not dropped
+- They appear in the unfinished/backlog list since they are still games the user may play
+- Unplayed games that are refunded DO count as **dropped** (refund signal overrides)
+
+### Multiple games per purchase
+- A purchase can have multiple games via `Purchase.games` (many-to-many)
+- A purchase is finished if ANY of its games is finished
+- A purchase is dropped if ANY of its games is abandoned OR the purchase itself is refunded
+
+### PlayEvents without ended date
+- A PlayEvent with `started` but no `ended` does NOT count as finished
+- This represents a game that was started but not completed
+
+### Retired games
+- Retired games (`status="r"`) are considered **dropped**
+- Retirement is for games the user intentionally removed from their collection (collector's items, no longer accessible, etc.)

games/migrations/0016_add_needs_price_update.py

@@ -0,0 +1,22 @@
+# Generated by Django 6.0.1 on 2026-05-12 11:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('games', '0015_alter_purchase_date_purchased_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='purchase',
+            name='needs_price_update',
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.RunSQL(
+            "UPDATE games_purchase SET needs_price_update = FALSE WHERE converted_price IS NOT NULL AND converted_currency != ''",
+            reverse_sql="UPDATE games_purchase SET needs_price_update = TRUE WHERE converted_price IS NOT NULL AND converted_currency != ''",
+        ),
+    ]

games/models.py

@@ -179,6 +179,7 @@ class Purchase(models.Model):
     price_currency = models.CharField(max_length=3, default="USD")
     converted_price = models.FloatField(null=True)
     converted_currency = models.CharField(max_length=3, blank=True, default="")
+    needs_price_update = models.BooleanField(default=True, db_index=True)
     price_per_game = GeneratedField(
         expression=Coalesce(F("converted_price"), F("price"), 0) / F("num_purchases"),
         output_field=models.FloatField(),
@@ -240,12 +241,6 @@ class Purchase(models.Model):
     def is_game(self):
         return self.type == self.GAME
 
-    def price_or_currency_differ_from(self, purchase_to_compare):
-        return (
-            self.price != purchase_to_compare.price
-            or self.price_currency != purchase_to_compare.price_currency
-        )
-
     def refund(self):
         self.date_refunded = timezone.now()
         self.save()
@@ -255,19 +250,6 @@ class Purchase(models.Model):
             raise ValidationError(
                 f"{self.get_type_display()} must have a related purchase."
             )
-        if self.pk is not None:
-            # Retrieve the existing instance from the database
-            existing_purchase = Purchase.objects.get(pk=self.pk)
-            # If price has changed, reset converted fields
-            if existing_purchase.price_or_currency_differ_from(self):
-                from games.tasks import currency_to
-
-                exchange_rate = get_or_create_rate(
-                    self.price_currency, currency_to, self.date_purchased.year
-                )
-                if exchange_rate:
-                    self.converted_price = floatformat(self.price * exchange_rate, 0)
-                    self.converted_currency = currency_to
         super().save(*args, **kwargs)
 
 

games/signals.py

@@ -17,6 +17,29 @@ from games.models import Game, GameStatusChange, Purchase, Session
 logger = logging.getLogger("games")
 
 
+@receiver(pre_save, sender=Purchase)
+def store_purchase_price_snapshot(sender, instance, **kwargs):
+    """Store old price values before save so we can detect changes."""
+    if instance.pk is not None:
+        try:
+            old_instance = sender.objects.get(pk=instance.pk)
+            instance._old_price = old_instance.price
+            instance._old_currency = old_instance.price_currency
+        except sender.DoesNotExist:
+            pass
+
+
+@receiver(post_save, sender=Purchase)
+def mark_needs_price_update(sender, instance, created, **kwargs):
+    """Mark purchase for price update if price or currency changed."""
+    if not created and hasattr(instance, "_old_price"):
+        if (
+            instance.price != instance._old_price
+            or instance.price_currency != instance._old_currency
+        ):
+            sender.objects.filter(pk=instance.pk).update(needs_price_update=True)
+
+
 @receiver(m2m_changed, sender=Purchase.games.through)
 def update_num_purchases(sender, instance, action, reverse, **kwargs):
     if not reverse and action.startswith("post_"):

games/tasks.py

@@ -1,6 +1,7 @@
 import logging
 
 import requests
+from django.db import models
 from django.template.defaultfilters import floatformat
 
 logger = logging.getLogger("games")
@@ -12,68 +13,77 @@ currency_to = "CZK"
 currency_to = currency_to.upper()
 
 
-def save_converted_info(purchase, converted_price, converted_currency):
+def _get_exchange_rate(currency_from, currency_to, year):
+    logger.debug(
+        f"[convert_prices]: Looking for exchange rate in database: {currency_from}->{currency_to}"
+    )
+    rate = ExchangeRate.objects.filter(
+        currency_from=currency_from, currency_to=currency_to, year=year
+    ).first()
+    if not rate:
+        logger.debug(
+            f"[convert_prices]: Getting exchange rate from {currency_from} to {currency_to} for {year}..."
+        )
+        try:
+            response = requests.get(
+                f"https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@{year}-01-01/v1/currencies/{currency_from.lower()}.json"
+            )
+            response.raise_for_status()
+            data = response.json()
+            currency_from_data = data.get(currency_from.lower())
+            rate = currency_from_data.get(currency_to.lower())
+            if rate:
+                logger.info(f"[convert_prices]: Got {rate}, saving...")
+                exchange_rate = ExchangeRate.objects.create(
+                    currency_from=currency_from,
+                    currency_to=currency_to,
+                    year=year,
+                    rate=floatformat(rate, 2),
+                )
+                rate = exchange_rate.rate
+            else:
+                logger.info("[convert_prices]: Could not get an exchange rate.")
+        except requests.RequestException as e:
+            logger.info(
+                f"[convert_prices]: Failed to fetch exchange rate for {currency_from}->{currency_to} in {year}: {e}"
+            )
+    elif rate:
+        rate = rate.rate
+    return rate
+
+
+def _save_converted_price(purchase, converted_price, needs_update):
     logger.info(
-        f"Setting converted price of {purchase} to {converted_price} {converted_currency} (originally {purchase.price} {purchase.price_currency})"
+        f"Setting converted price of {purchase} to {converted_price} {currency_to} (originally {purchase.price} {purchase.price_currency})"
     )
     purchase.converted_price = converted_price
-    purchase.converted_currency = converted_currency
+    purchase.converted_currency = currency_to
-    purchase.save()
+    if needs_update:
+        purchase.needs_price_update = False
+    purchase.save(update_fields=["converted_price", "converted_currency", "needs_price_update"])
 
 
 def convert_prices():
     purchases = Purchase.objects.filter(
-        converted_price__isnull=True, converted_currency=""
+        models.Q(needs_price_update=True) | models.Q(converted_price__isnull=True)
-    )
+    ).distinct()
     if purchases.count() == 0:
         logger.info("[convert_prices]: No prices to convert.")
+        return
 
     for purchase in purchases:
+        needs_update = purchase.needs_price_update
         if purchase.price_currency.upper() == currency_to or purchase.price == 0:
-            save_converted_info(purchase, purchase.price, currency_to)
+            _save_converted_price(purchase, purchase.price, needs_update)
             continue
         year = purchase.date_purchased.year
         currency_from = purchase.price_currency.upper()
-
+        rate = _get_exchange_rate(currency_from, currency_to, year)
-        exchange_rate = ExchangeRate.objects.filter(
+        if rate:
-            currency_from=currency_from, currency_to=currency_to, year=year
+            _save_converted_price(
-        ).first()
-        logger.info(
-            f"[convert_prices]: Looking for exchange rate in database: {currency_from}->{currency_to}"
-        )
-        if not exchange_rate:
-            logger.info(
-                f"[convert_prices]: Getting exchange rate from {currency_from} to {currency_to} for {year}..."
-            )
-            try:
-                # this API endpoint only accepts lowercase currency string
-                response = requests.get(
-                    f"https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@{year}-01-01/v1/currencies/{currency_from.lower()}.json"
-                )
-                response.raise_for_status()
-                data = response.json()
-                currency_from_data = data.get(currency_from.lower())
-                rate = currency_from_data.get(currency_to.lower())
-
-                if rate:
-                    logger.info(f"[convert_prices]: Got {rate}, saving...")
-                    exchange_rate = ExchangeRate.objects.create(
-                        currency_from=currency_from,
-                        currency_to=currency_to,
-                        year=year,
-                        rate=floatformat(rate, 2),
-                    )
-                else:
-                    logger.info("[convert_prices]: Could not get an exchange rate.")
-            except requests.RequestException as e:
-                logger.info(
-                    f"[convert_prices]: Failed to fetch exchange rate for {currency_from}->{currency_to} in {year}: {e}"
-                )
-        if exchange_rate:
-            save_converted_info(
                 purchase,
-                floatformat(purchase.price * exchange_rate.rate, 0),
+                floatformat(purchase.price * rate, 0),
-                currency_to,
+                needs_update,
             )
 
 

games/tests.py

@@ -1,3 +1,102 @@
+from datetime import date
+
 from django.test import TestCase
 
-# Create your tests here.
+from games.models import Game, Platform, Purchase
+from games.tasks import convert_prices
+
+
+class PurchaseNeedsPriceUpdateTest(TestCase):
+    def setUp(self):
+        self.platform = Platform.objects.create(name="PC", icon="pc", group="PC")
+        self.game = Game.objects.create(name="Test Game", platform=self.platform)
+
+    def test_new_purchase_has_needs_price_update_true(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        self.assertTrue(purchase.needs_price_update)
+
+    def test_convert_prices_sets_flag_to_false(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        self.assertTrue(purchase.needs_price_update)
+
+        convert_prices()
+
+        purchase.refresh_from_db()
+        self.assertFalse(purchase.needs_price_update)
+
+    def test_price_change_sets_needs_price_update(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        purchase.converted_price = 1000
+        purchase.converted_currency = "CZK"
+        purchase.needs_price_update = False
+        purchase.save()
+
+        purchase.price = 60.0
+        purchase.save()
+        purchase.refresh_from_db()
+        self.assertTrue(purchase.needs_price_update)
+
+    def test_currency_change_sets_needs_price_update(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        purchase.converted_price = 1000
+        purchase.converted_currency = "CZK"
+        purchase.needs_price_update = False
+        purchase.save()
+
+        purchase.price_currency = "EUR"
+        purchase.save()
+        purchase.refresh_from_db()
+        self.assertTrue(purchase.needs_price_update)
+
+    def test_name_change_does_not_set_needs_price_update(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        purchase.converted_price = 1000
+        purchase.converted_currency = "CZK"
+        purchase.needs_price_update = False
+        purchase.save()
+
+        purchase.name = "New Name"
+        purchase.save()
+        purchase.refresh_from_db()
+        self.assertFalse(purchase.needs_price_update)
+
+    def test_convert_prices_skips_already_converted(self):
+        purchase = Purchase.objects.create(
+            price=50.0,
+            price_currency="USD",
+            date_purchased=date(2025, 1, 1),
+        )
+        purchase.games.add(self.game)
+        purchase.converted_price = 1000
+        purchase.converted_currency = "CZK"
+        purchase.needs_price_update = False
+        purchase.save()
+
+        convert_prices()
+        purchase.refresh_from_db()
+        self.assertFalse(purchase.needs_price_update)